1. Field of the Invention
This disclosure generally relates to cooling systems for machines including induction motors and/or generators, and more particularly to a system and method for detecting a cooling system failure.
2. Description of the Related Art
The “fuel” powering an alternating current machine, such as a field-oriented induction motor, is current. This current may be divided into two components, torque current and flux current. Torque current may be viewed as that component of the current that generates motive force, or torque. Flux current may be viewed as that component of the current that generates magnetic flux in the rotor of the machine. Torque and flux currents in induction motors are discussed in more detail in co-pending U.S. patent application Ser. No. 10/345,872, filed Jan. 15, 2003, and entitled “OVERMODULATION SYSTEMS AND METHODS FOR INDUCTION MOTOR CONTROL” and in a February 1998 publication by Texas Instruments Europe bearing Literature No. BPRA073 and entitled Field Oriented Control of 3-Phase AC-Motors, which are incorporated herein by reference in their entirety.
Alternating current machines, such as induction motors and/or generators are often employed in electric and hybrid vehicles, which typically employ batteries and/or fuel cells as a power source. Current is supplied to windings through a power subsystem, typically comprising an inverter. Power subsystems typically employ power semiconductor devices, such as insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), and/or semiconductor diodes. These power semiconductor devices dissipate large amounts of heat during high power operation, creating thermal management problems which may limit the operating range, increase cost, increase size and/or weight, adversely effect efficiency, and/or reduce reliability of the power subsystem. Heat is also generated in the windings. This heat can cause the components to fail, and thus must be addressed. Cooling systems may employ a coolant. Exemplary cooling systems are described in co-pending U.S. patent application Ser. Nos. 10/738,926 filed Dec. 16, 2003 and entitled “POWER MODULE WITH HEAT EXCHANGE” and U.S. patent application Ser. No. 10/861,319 filed Jun. 4, 2004, and entitled “INTERLEAVED POWER CONVERTER,” which are incorporated herein by reference in their entirety.
Cooling systems may not be installed properly or may fail or malfunction. For example, a fan may not be connected or may malfunction, a coolant line may be blocked or disconnected, or a coolant level may be too low. If the cooling system fails or malfunctions, damage to components of a system, such as the power module and/or the alternating current machine, may occur. Therefore it can be appreciated that a system and method to detect cooling system failure is highly desirable.